Diels-Alder crosslinkable dendritic nonlinear optic chromophores and polymer composites

ABSTRACT

Diels-Alder crosslinkable dendritic nonlinear optical chromophore compounds, films and crosslinked polymer composites formed from the chromophore compounds, methods for making and using the chromophore compounds, films, and crosslinked polymer composites, and electro-optic devices that include films and crosslinked polymer composites formed from the chromophore compounds.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 61/056,761, filed May 28, 2008, expressly incorporatedherein by reference in its entirety.

STATEMENT OF GOVERNMENT LICENSE RIGHTS

This invention was made with Government support under Contract No.DMR0120967 awarded by the National Science Foundation, and Contract No.N00014-06-0859 awarded by the Office of Naval Research. The Governmenthas certain rights in the invention.

BACKGROUND OF THE INVENTION

Extensive research to produce oriented nonlinear optical (NLO)chromophores exhibiting large electro-optic (EO) activity and goodthermal stability has been pursued for years. Recent studies showed thateffective site isolation and molecular assembly are critical forimproving the performance of such materials. In newly reported dendriticmolecular glasses, chromophores with large hyperpolarizability (βμ) areselectively functionalized and self-assembled into well-definedarchitectures, leading to materials with high poling-induced acentricorder and large EO coefficients (r₃₃ values of up to 100-300 pm/V at thewavelength of 1310 nm). These materials provides an effective platformto build innovative optical devices, such as low-V_(π) Mach-Zenderinterferometers, EO ring resonators, and polymer-silicon slottedwaveguide modulators. Although the progress is encouraging, it isbelieved that greater impact could be accomplished for high-speedinformation processing if the well-established semiconductor processesfor microelectronics could be applied to photonics. High speedprocessing will provide a boost to the development of devices forurgently needed high bandwidth information processing. In order tofulfill this, materials need to meet numerous stringent requirements inmanufacturing, assembly, and end-use environments of devices. Therefore,the search for organic E-O materials with sufficient r₃₃ values andexcellent thermal stability is an ongoing challenge.

The poling induced polar order of large βμ chromophores in any organicspin-on materials must withstand prolonged operation temperatures of upto 100° C., and brief temperature excursions during processing that mayexceed 250° C. To date, many studies have been performed on improvingone or some of these required properties. However, none of the materialsdeveloped to date meet all of the above criteria. Furthermore, thethermal stability and decomposition mechanisms of new generation ofhighly polarizable chromophores are not well understood.

The intrinsic stability of typical high-r₃₃ E-O dendrimers and binarypolymers under high temperature (up to 200° C.) has been investigated.These materials often contain high concentrations of chemicallysensitive chromophores, which are spaced apart by either physical π-πinteractions or “loosely” crosslinked polymeric networks containingflexible tether groups. Most of these materials have relatively low tomoderate glass transition temperatures (T_(g)), and are only thermallystable enough (85-150° C.) to satisfy the basic fabrication andoperation of conventional optical modulators.

However, rapid decomposition of chromophores is often observed for thesematerials under higher temperatures. From both thermal and spectroscopicanalysis of a standardized dipolar chromophore,2-[4-(2-{5-[2-(4-{bis-[2-(tert-butyl-dimethyl-silanyloxy)-ethyl]-amino}-phenyl)-vinyl]-thiophen-2-yl}-vinyl)-3-cyano-5-methyl-5-trifluoromethyl-5H-furan-2-ylidene]malononitrile (AJL8), it was found that a bimolecular reaction mechanismis responsible for the initial decomposition of the chromophore. Thedetailed mechanism for site-specific reactivity of NLO chromophores hasnot been well understood, and therefore optimization of organic E-Omaterials for high temperature applications has been impaired.

A need exists for E-O materials with acceptable r₃₃ values that alsohave thermal stability sufficient for manufacturing, assembly, andend-use environments of electro-optic devices. The present inventionseeks to fulfill this need and provides further related advantages.

SUMMARY OF THE INVENTION

The present invention provides Diels-Alder (DA) crosslinkable dendriticnonlinear optical (NLO) chromophore compounds, films and crosslinkedpolymer composites formed from the DA crosslinkable dendriticchromophores, methods for making and using the DA crosslinkabledendritic chromophores, films, and crosslinked polymer composites, andelectro-optic devices that include films and crosslinked polymercomposites formed from the DA crosslinkable dendritic chromophores.

In one aspect, the invention provides DA crosslinkable dendriticchromophore compounds. In one embodiment, the invention provides acompound having the formula (I):

wherein D is a π-electron donor group; A is a π-electron acceptor group;D₁ is a dendron moiety functionalized with one or more crosslinkablegroups; D₂ is a dendron moiety functionalized with one or morecrosslinkable groups; n is 0, 1, or 2; m is 0, 1, or 2; and m+n is ≧1;wherein the crosslinkable groups are independently selected from thegroup consisting of an anthracenyl group and an acrylate group.

In one embodiment, the crosslinkable groups are anthracenyl groups.

In one embodiment, the crosslinkable groups are acrylate groups.

In one embodiment, the crosslinkable groups are anthracenyl and acrylategroups.

In one embodiment, D₁ and D₂ are independently selected from the groupconsisting of

In one embodiment, D₁ is d1 and D₂ is d1.

In one embodiment, D₁ is d2 and D₂ is d2.

In one embodiment, D₁ is d1 and D₂ is d2.

In one embodiment, D₁ is d2 and D₂ is d1.

In another aspect, the invention provides methods for forming a film orcomposite having electro-optic activity.

In one embodiment, the method comprises:

(a) depositing first and second compounds of the invention onto asubstrate to provide a film, wherein the first compound has one or moreanthracenyl groups, and wherein the second compound has one or moreacrylate groups;

(b) applying an aligning force to the film at a temperature sufficientto provide a film having at least a portion of the compounds aligned;

(c) heating the film having at least a portion of the compounds alignedat a temperature sufficient to effect crosslinking between the first andsecond compounds; and

(d) reducing the temperature of the film to provide a hardened filmhaving electro-optic activity.

In one embodiment, the method further comprises depositing acrosslinkable crosslinking agent on the substrate.

In one embodiment, the method further comprises depositing acrosslinkable polymer on the substrate.

In another embodiment, the invention provides a method for forming afilm having electro-optic activity, comprising:

(a) depositing a crosslinkable compound of the invention onto asubstrate to provide a film, wherein the compound has one or moreanthracenyl groups and one or more acrylate groups;

(b) applying an aligning force to the film at a temperature sufficientto provide a film having at least a portion of the compounds aligned;

(c) heating the film having at least a portion of the compounds alignedat a temperature sufficient to effect crosslinking; and

(d) reducing the temperature of the film to provide a hardened filmhaving electro-optic activity.

In one embodiment, the method further comprises depositing acrosslinkable crosslinking agent on the substrate.

In one embodiment, the method further comprises depositing acrosslinkable polymer on the substrate.

In another aspect, the invention provides films or composites formed bythe above methods.

In a further aspect, the invention provides electro-optic that includethe films or composites of the invention.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same become betterunderstood by reference to the following detailed description, whentaken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic illustration of a tandem Diels-Alder andretro-Diels-Alder decomposition pathway for a thiophene-bridgednonlinear optical chromophore (AJL8);

FIG. 2 is an analysis of the chemical instability of a thiophene-bridgednonlinear optical chromophore (ALJ8);

FIG. 3 is a differential scanning calorimetry (DSC) curve for athiophene-bridged nonlinear optical chromophore (AJL8);

FIG. 4 is a thermogravimetric analysis (TGA) curve for athiophene-bridged nonlinear optical chromophore (AJL8);

FIG. 5 compares the absorption spectra of pristine AJL8, AJL8 afterthermal curing (ramp to 200° C. at the rate of 10° C./min and kept atthis temperature for 5 min under nitrogen), and decomposition byproductchromophore 1 (structure inserted) in THF. The concentration has beennormalized to be 0.67 mg/mL.

FIG. 6 is a schematic illustration of representative thiophene-bridgednonlinear optical chromophores of the invention (DA crosslinkabledendrimers 5 and 6) and a dienophile crosslinker (TAC) useful for makingfilms of the invention. The DA crosslinked adduct is illustrated in theinsert; and

FIG. 7 compares differential scanning calorimetry (DSC) curves for TAC,DA crosslinkable dendrimer 5, and blend 5/TAC before and after curing at10° C./min under nitrogen.

FIG. 8 compares the UV-vis-NIR absorption spectra of thin films of 5/TACupon thermal curing (150° C. for 30 min, 180° C. for 30 min, 200° C. for30 min, 230° C. for 30 min. Spectra are normalized to initial absorptionpeak.

FIG. 9 compares the UV-vis-NIR absorption spectra of thin films of DAcrosslinkable dendrimer 5 upon thermal curing (150° C. for 30 min, 180°C. for 30 min, 200° C. for 30 min, 230° C. for 30 min). Spectra arenormalized to initial absorption peak.

FIG. 10 is a schematic illustration of the preparation of firstgeneration reactive dendrons A5 (anthracenyl) and A8 (acrylate) anddienophile crosslinking agent TAC.

FIG. 11 is a schematic illustration of the preparation of representativeDA crosslinkable dendrimers (5 and 6) of the invention.

FIGS. 12A and 12B are schematic illustrations of the preparations ofrepresentative crosslinkable polymers having pendant anthracenyl groups(PMMA-AMA30) (12A) and (AJL4B) (12B) useful in making films of theinvention.

FIG. 13 is a schematic illustration of the preparation of representativepolymer composites of the invention from crosslinkable polymers havingpendant anthracenyl groups (PMMA-AMA30 and AJL4B) and DA crosslinkabledendrimers having acrylate-functionalized dendrons (AJLS113, AJLS109,and AJLS114).

FIG. 14 compares the UV-vis-NIR absorption spectra of thin films ofPMMA-AMA30/AJLS109 upon thermal curing (150° C. for 30 min, 180° C. for30 min, 200° C. for 30 min).

FIG. 15 compares the UV-vis-NIR absorption spectra of thin films ofPMMA-AMA30/AJLS114 upon thermal curing (150° C. for 30 min, 180° C. for30 min, 200° C. for 30 min).

FIG. 16 is a schematic illustration of a representativethiophene-bridged nonlinear optical chromophores of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides Diels-Alder (DA) crosslinkable dendriticnonlinear optical (NLO) chromophore compounds, films and crosslinkedpolymer composites formed from the DA crosslinkable dendriticchromophores, methods for making and using the DA crosslinkabledendritic chromophores, films, and crosslinked polymer composites, andelectro-optic devices that include films and crosslinked polymercomposites formed from the DA crosslinkable dendritic chromophores.

In one aspect, the invention provides DA crosslinkable dendriticchromophore compounds. The chromophore compounds of the invention arecrosslinkable by virtue of crosslinkable moieties that functionalize thecompounds. The chromophore compounds include crosslinkable moieties thatare reactive toward Diels-Alder (4+2) cycloaddition. The chromophorecompounds crosslinkable moieties include diene moieties and dienophilemoieties. Individual crosslinkable chromophore compounds of theinvention can include both diene moieties and dienophile moieties. Thechromophore compounds' diene and dienophile moieties are reactive towardother compounds (e.g., DA crosslinkable chromophore compounds, DAcrosslinkable polymers, and DA crosslinking agents) having appropriateDA reactivity (i.e., a DA crosslinkable chromophore compound having oneor more diene moieties is DA reactive toward a compound having one ormore dienophile moieties; a DA crosslinkable chromophore compound havingone or more dienophile moieties is DA reactive toward a compound havingone or more diene moieties; and a DA crosslinkable chromophore compoundhaving one or more diene moieties and one or more dienophile moieties isDA reactive toward like compounds as well as a compound having one ormore diene moieties or a compound having one or more dienophilemoieties). As used herein, the terms “chromophore compounds(s)” and“chromophore(s)” are used interchangeably.

The DA crosslinkable chromophore compounds of the invention aredendritic compounds. As used herein, the term “dendritic compound”refers to a compounds that includes one or more dendrons. The dendronsare functionalized with one or more DA crosslinkable moieties (i.e.,diene or dienophile). The chromophore compounds of the invention areprovided by incorporation of one or more functionalized dendrons. Thechromophore compounds of the invention are D-π₁-B-π₂-A (“push-pull”chromophores) in which an electron donor group (D) is electronicallyconjugated to an electron acceptor group (A) through a bridge group (B)optionally via π-bridges π₁ and π₂. In one embodiment, the chromophorecompound of the invention has a dendron functionalized with acrosslinkable moiety covalently coupled to the compound's donor group(D). In one embodiment, the chromophore compound of the invention has adendron functionalized with a crosslinkable moiety covalently coupled tothe compound's bridge group (B). In one embodiment, the chromophorecompound of the invention has a dendron functionalized with acrosslinkable moiety covalently coupled to the compound's donor group(D) and bridge (B) group.

The DA crosslinkable dendritic chromophore compounds of the inventioninclude one or more diene or one or more dienophile moieties. In oneembodiment, the diene moieties are anthracene moieties. In oneembodiment, the dienophile moieties are acrylate moieties. The compoundsof the invention do not include dienophile moieties that are maleimidemoieties. Representative dendrons useful for incorporating thesecrosslinkable moieties into the chromophore compounds of the inventioninclude d1 and d2 shown below.

Dendron d1 includes two anthracenyl moieties and dendron d2 includes twoacrylate moieties. The anthracenyl moiety is reactive toward theacrylate moiety to form a DA (4+2) adduct (or crosslink) as illustratedin FIG. 6. It will be appreciated that dendrons, other than d1 and d2,that include one or more anthracenyl and one or more acrylate moieties,respectively, can be prepared and advantageous utilized in thepreparation of the DA crosslinkable dendritic chromophore compounds ofthe invention.

In one embodiment, the DA crosslinkable dendritic chromophore compoundof the invention is a thiophene-bridged chromophore compound having theformula (I)

wherein D is a π-electron donor group, A is a π-electron acceptor group,D₁ is a dendron moiety functionalized with one or more crosslinkablegroups, D₂ is a dendron moiety functionalized with one or morecrosslinkable groups, n is 0, 1, or 2, m is 0, 1, or 2, and m+n is ≧1,wherein the crosslinkable group is independently selected from the groupconsisting of an anthracenyl group and an acrylate group.

In one embodiment, D₁ and D₂ are the same and the crosslinkable group isan anthracenyl group.

In one embodiment, D₁ and D₂ are the same and the crosslinkable group isan acrylate group.

In one embodiment, D₁ and D₂ are different and the D₁ crosslinkablegroup is an anthracenyl group and the D₂ crosslinkable group is anacrylate group.

In one embodiment, D₁ and D₂ are different and the D₁ crosslinkablegroup is an acrylate group and the D₂ crosslinkable group is ananthracenyl group.

In one embodiment, D₁ is d1, D₂ is d1, n is 1, and m is 1.

In one embodiment, D₁ is d1, D₂ is d1, n is 1, and m is 0.

In one embodiment, D₁ is d1, D₂ is d1, n is 0, and m is 1.

In one embodiment, D₁ is d2, D₂ is d2, n is 1, and m is 1.

In one embodiment, D₁ is d2, D₂ is d2, n is 1, and m is 0.

In one embodiment, D₁ is d2, D₂ is d2, n is 0, and m is 1.

In one embodiment, D₁ is d1, D₂ is d2, n is 1, and m is 1.

In one embodiment, D₁ is d1, D₂ is d2, n is 1, and m is 0.

In one embodiment, D₁ is d1, D₂ is d2, n is 0, and m is 1.

In one embodiment, D₁ is d2, D₂ is d1, n is 1, and m is 1.

In one embodiment, D₁ is d2, D₂ is d1, n is 1, and m is 0.

In one embodiment, D₁ is d2, D₂ is d1, n is 0, and m is 1.

In certain embodiments, the DA crosslinkable compound includes dienemoieties. In these embodiments, the compound includes one or moredendrons functionalized with anthracenyl moieties. In one embodiment,the DA crosslinkable compound includes an anthracenyl-containing dendroncovalently coupled to the chromophore's donor group. In one embodiment,the DA crosslinkable compound includes an anthracenyl-containing dendroncovalently coupled to the chromophore's thiophene group. In oneembodiment, the DA crosslinkable compound includes ananthracenyl-containing dendrons covalently coupled to each of thechromophore's donor and thiophene groups.

A representative DA crosslinkable compound of the invention thatincludes only diene crosslinkable groups is illustrated in FIG. 6 (seeanthracenyl-containing compound 5).

In certain embodiments, the DA crosslinkable compound includesdienophile moieties. In these embodiments, the compound includes one ormore dendrons functionalized with acrylate moieties. In one embodiment,the DA crosslinkable compound includes an acrylate-containing dendroncovalently coupled to the chromophore's donor group. In one embodiment,the DA crosslinkable compound includes an acrylate-containing dendroncovalently coupled to the chromophore's thiophene group. In oneembodiment, the DA crosslinkable compound includes anacrylate-containing dendrons covalently coupled to each of thechromophore's donor and thiophene groups.

A representative DA crosslinkable compound of the invention thatincludes only dienophile crosslinkable groups is illustrated in FIG. 6(see acrylate-containing compound 6).

In certain embodiments, the DA crosslinkable compound includes diene anddienophile moieties. In these embodiments, the compound includes one ormore dendrons functionalized with anthracenyl moieties and one or moredendrons functionalized with acrylate moieties. In one embodiment, theDA crosslinkable compound includes an anthracenyl-containing dendroncovalently coupled to the chromophore's donor group and anacrylate-containing dendron covalently coupled to the chromophore'sthiophene group. In one embodiment, the DA crosslinkable compoundincludes an anthracenyl-containing dendron covalently coupled to thechromophore's thiophene group and an acrylate-containing dendroncovalently coupled to the chromophore's donor group.

A representative DA crosslinkable compound of the invention thatincludes diene and dienophile crosslinkable groups is illustrated inFIG. 16.

The nature of the dendron and its covalent coupling to the chromophoreis not critical. Suitable dendrons are carboxylic acids and are readilycovalently coupled to a chromophore through hydroxyl groups (e.g.,—(CH₂)_(n)OH) present in the chromophore.

The DA crosslinkable dendritic chromophore compounds of the inventioninclude a π-electron donor group (D) electronically conjugated to aπ-electron acceptor group (A) through π-electron bridge group thatincludes a thiophene group (see formula (I)). As used herein,“π-electron donor group” (represented by D) is an atom or group of atomswith low electron affinity relative to an acceptor (represented by A,defined below) such that, when the donor is conjugated to an acceptorthrough a π-electron bridge group, electron density is transferred fromthe donor to the acceptor. A “π-electron acceptor group” (represented byA) is an atom or group of atoms with high electron affinity relative toa donor such that, when the acceptor is conjugated to a donor through aπ-electron bridge, electron density is transferred from the acceptor tothe donor.

The nature of the donor group (D) and acceptor group (A) in thecompounds of the invention (formula (I)) is not critical. Donor andacceptor groups for D-π-A (“push-pull”) chromophores are known to thoseof skill in the art and can be readily incorporated into the compoundsof the invention by standard synthetic methodologies.

Representative donor groups include diarylamino (e.g., —N(C₆H₅)₂),dialkylamino (e.g., —N(C₂H₅)₂), and arylalkylamino groups. Thediarylamino, dialkylamino, and arylalkylamino groups can be furthersubstituted to include, for example, crosslinkable groups and/ordendrons. Representative donor groups include dialkylamino groups havingthe formula:

wherein n and m are independently an integer from 1 to 6, and A and Bare independently selected from hydrogen, methyl, or OR, where R ishydrogen, C1-C6 alkyl, aryl (e.g., phenyl), acyl (e.g., —C(═O)—R, whereR is C1-C10), a silyl group (e.g., trimethylsilyl,t-butyldimethylsilyl), a crosslinkable group, or a dendron optionallysubstituted with a crosslinkable group, and * represents the point ofattachment.

Representative acceptor groups include furanylidene groups, such astricyanofuranylidene groups. Representative acceptor groups includefuranylidene groups having the formula:

wherein R_(a1) and R_(a2) are independently selected from alkyl (e.g.,branched and straight chain C1-C12), fluorinated alkyl, perfluorinatedalkyl (e.g., CF₃), and substituted alkyl; aryl (e.g., phenyl),fluorinated aryl, perfluorinated aryl (e.g., C₆F₅), and substitutedaryl; and heteroaryl (e.g., thiophenyl) and substituted heteroaryl; andX₁, X₂, and X₃ are independently selected from electronegative atoms orgroups such as fluoro (F), cyano (CN), trifluoromethyl (CF₃), andtrifluoromethylsulfonyl (SO₂CF₃), and * represents the point ofattachment.

Representative donor and acceptor groups useful in the compounds of theinvention are described in U.S. Pat. Nos. 5,290,630; 5,708,178;6,067,186; 6,090,332; 7,014,796; 7,029,606; 7,078,542; 7,144,960;7,268,188; 7,307,173; 7,425,643; 7,507,840; and U.S. patent applicationSer. Nos. 11/952,747, filed Dec. 7, 2007; Ser. No. 11/952,737, filedDec. 7, 2007; Ser. No. 11/462,339, filed Aug. 3, 2006; Ser. No.11/462,343, filed Aug. 3, 2006; and Ser. No. 10/212,473, filed Aug. 2,2002, each incorporated herein by reference in its entirety.Representative donor and acceptor groups useful in the compounds of theinvention are illustrated in FIGS. 1, 2, 6, 11, and 13.

Representative DA crosslinkable dendritic chromophore compounds of theinvention are illustrated in FIG. 6 (see compounds 5 and 6) and theirpreparations described in Example 1.

The chromophore compounds of the invention generally have highelectro-optic coefficients; large hyperpolarizability; large dipolemoments; chemical, thermal, electrochemical, and photochemicalstability; low absorption at operating wavelengths (e.g., 1.3 and 1.55μm); and suitable solubility in solvents used for making the composites.

Nonlinear optical activity of chromophore compounds depends mainly onthe compound's hyperpolarizability (β). A measure of a compound'snonlinearity is μβ, where μ is the compound's dipole moment. Acompound's optical nonlinearity (μβ) can be measured as described inDalton et al., “Importance of Intermolecular Interactions in theNonlinear Optical Properties of Poled Polymers”, Applied PhysicsLetters, Vol. 76, No. 11, pp. 1368-1370 (2000).

A compound or composite's electro-optic coefficient (r₃₃) can bemeasured using attenuated total reflection (ATR) technique attelecommunication wavelengths of 1.3 or 1.55 μm. A representative methodfor measuring the electro-optic coefficient is described in Dalton etal., “Importance of Intermolecular Interactions in the Nonlinear OpticalProperties of Poled Polymers”, Applied Physics Letters, Vol. 76, No. 11,pp. 1368-1370 (2000).

The chromophore compounds of the invention can be advantageous formedinto films or composites having EO activity and used in EO devices.Thus, in another aspect, the present invention provides a film (orcomposite) formed from a DA crosslinkable dendritic chromophore compoundof the invention. In one embodiment, the films or composites of theinvention are formed by crosslinking a first chromophore compound of theinvention having one or more diene groups and a second chromophorecompound of the invention having one or more dienophile groups toprovide a crosslinked polymer composite. In another embodiment, thefilms or composites of the invention are formed by crosslinking acrosslinkable chromophore compound of the invention having one or morediene groups and one or more dienophile groups to provide a crosslinkedpolymer composite. Alternatively, the films or composites of theinvention are formed by crosslinking one or more chromophore compoundsof the invention with a DA crosslinkable polymer and/or a DAcrosslinkable crosslinking agent.

In one embodiment, the films or composites of the invention do notinclude non-crosslinkable host materials or other non-crosslinkablecomponents (e.g., D-π-A (“push-pull”) chromophores). In otherembodiments, the films or composites can include non-crosslinkable hostmaterials or other non-crosslinkable components.

Suitable crosslinkable polymers useful in making the films andcomposites of the invention include polymers having pendant diene groups(e.g., anthracenyl groups) or polymers having pendant dienophile groups(e.g., acrylate groups). Polymers having pendant diene groups are DAreactive with DA crosslinkable chromophore compounds of the inventionhaving dienophile groups (e.g., acrylate groups) to provide crosslinkedpolymer films or composites. Similarly, polymers having pendantdienophile groups are DA reactive with DA crosslinkable chromophorecompounds of the invention having diene groups (e.g., anthracenylgroups) to provide crosslinked polymer films or composites. Thesecrosslinkable polymers are not crosslinkable chromophore compounds.

Representative DA crosslinkable polymers useful for making the films orcomposites of the invention include anthracenyl-containing polymersPMMA-AMA30 and AJL4B illustrated in FIGS. 12A and 12B, respectively.

Suitable crosslinkable crosslinking agents useful in making the filmsand composites of the invention include compounds having two or morediene groups (e.g., anthracenyl groups) or two or more dienophile groups(e.g., acrylate groups). Crosslinking agents diene groups are DAreactive with DA crosslinkable chromophore compounds of the inventionhaving dienophile groups (e.g., acrylate groups) to provide crosslinkedpolymer films or composites. Similarly, crosslinking agents havingdienophile groups are DA reactive with DA crosslinkable chromophorecompounds of the invention having diene groups (e.g., anthracenylgroups) to provide crosslinked polymer films or composites. Thesecrosslinking agents are not crosslinkable chromophore compounds.

A representative DA crosslinkable crosslinking agent is TAC:

The product films or composites of the invention have 4+2 cycloadditionadduct crosslinks formed from cycloaddition of anthracenyl and acrylategroups. When only DA crosslinkable chromophore compounds are formed intothe film or composite, the product film or composite includes a network(or plurality) of dendritic chromophore compounds covalently coupledthrough 4+2 cycloaddition adduct crosslinks. When the film or compositeis further formed by the inclusion of one or more of a DA crosslinkablecrosslinking agent and/or a DA crosslinkable polymer, the product filmor composite includes a network (or plurality) of dendritic chromophorecompounds, crosslinking agent, and/or polymer covalently coupled through4+2 cycloaddition adduct crosslinks.

Films can be created by spin coating solutions including the compoundsof the invention onto a substrate, optionally with a suitable DAcrosslinkable crosslinking agent and/or suitable DA crosslinkablepolymer. Compounds of the invention are generally soluble in solventuseful for spin coating including chloroform, cyclopentanone,1,1,2-trichloroethane, and THF. Pinhole free thin films can be preparedby spin coating directly from 1,1,2-trichloroethane solution. The filmsurfaces are typically highly uniform as measured by atomic forcemicroscopy (typically about 0.5 nm of root-mean-squared roughness). Theamount of chromophore compound in the film (i.e., chromophore density byweight percent) can vary depending on the chromophores used and the EOproperties desired. In one embodiment, the film includes about 10 weightpercent chromophore. In one embodiment, the film includes about 20weight percent chromophore. In one embodiment, the film includes about30 weight percent chromophore. In one embodiment, the film includesabout 40 weight percent chromophore. In one embodiment, the filmincludes about 50 weight percent chromophore. In one embodiment, thefilm includes include about 60 weight percent chromophore. In oneembodiment, the film includes about 70 weight percent chromophore. Inone embodiment, the film includes about 80 weight percent chromophore.In one embodiment, the film includes about 90 weight percentchromophore.

In another aspect, the present invention provides a method for forming afilm or composite from chromophore compounds of the invention,optionally with a suitable DA crosslinkable crosslinking agent and/orsuitable DA crosslinkable polymer, to provide a film or composite inwhich at least a portion of the chromophores are aligned. The methodincludes depositing a chromophore compound of the invention, andoptionally a suitable DA crosslinkable crosslinking agent and/orsuitable DA crosslinkable polymer, onto a substrate; subjecting thedeposited materials to a temperature that is equal to or greater thanthe glass transition temperature of the compound or other materials;applying an aligning force to the deposited materials subjected toelevated temperature to align the chromophore compounds and to effectcrosslinking; and reducing the temperature of the composite below theglass transition temperature of the chromophore composite to provide ahardened, at least partially aligned chromophore film.

A representative embodiment of this method includes dissolving thechromophore compound, and optionally suitable DA crosslinkablecrosslinking agent and/or suitable DA crosslinkable polymer, in asuitable solvent; spin coating the solvated materials onto a suitablesubstrate, such as glass, semiconductor, or metal; evaporating anyremaining solvent to provide a film (or composite); heating the film(e.g., at or above the glass transition temperature of the filmcomponents), applying an electric field (i.e., poling) to align at leasta portion of the deposited chromophore compounds and to effectcrosslinking; and cooling the composite (e.g., below the glasstransition temperature of the composite) to provide the product film.This is only a representative method and many variations are possible ineach step. For example, a film components can be deposited from thesolid phase by evaporation; the components can be deposited at atemperature above the glass transition temperature of the composite,thus eliminating the heating requirement; or a magnetic or molecular(e.g., self-assembly) force could be used as an aligning force.

In one embodiment, the aligning force comprises an electric field. Arepresentative field is between 0.2 MV/cm and 1.5 MV/cm. Corona polingcan also be used as a means for electrostatic poling. Poling techniquesare well known to those skilled in the art.

When a chromophore film is at least partially aligned, some of theindividual chromophore molecules within the film will benon-centrosymmetrically aligned. The direction of alignment in arepresentative film will have a relationship to the aligning force. Inone representative embodiment, the chromophore molecules will align inthe direction of an electric poling field.

In one embodiment, the method for forming the film (or composite) havingEO activity includes:

(a) depositing a chromophore compound of the invention and optionally asuitable DA crosslinkable crosslinking agent and/or suitable DAcrosslinkable polymer onto a substrate to provide a film;

(b) applying an aligning force to the film at a temperature equal to orgreater than the glass transition of the compound and/or optionalcrosslinking agent or polymer to align at least a portion of thecompounds in the film;

(c) heating the film having at least a portion of the compounds alignedat a temperature sufficient to effect crosslinking between compounds orbetween compounds and optional crosslinking agent or polymer; and

(d) reducing the temperature of the film below the glass transitiontemperature of the compound and/or optional crosslinking agent orpolymer to provide a hardened film having at least a portion of thecompounds aligned in the film, thereby providing a film havingelectro-optic activity.

In a further aspect, the present invention provides electro-opticdevices formed from a DA crosslinkable chromophore compound of theinvention or a film (or composite) described above formed from achromophore compound of the invention. The chromophore compounds of theinvention, their composites, and methods described herein can be usefulin a variety of electro-optic applications. As used herein, the term“composite” refers to a crosslinked combination of one or morechromophore compounds of the invention, or a crosslinked combination ofone or more compounds of the invention with a suitable DA crosslinkablecrosslinking agent and/or a suitable DA crosslinkable polymer. Inaddition, the chromophore compounds, their composites, and relatedmethods may be applied to polymer transistors or other active or passiveelectronic devices, as well as OLED (organic light emitting diode) orLCD (liquid crystal display) applications.

The use of organic polymers in integrated optics and opticalcommunication systems containing optical fibers and routers has beenpreviously described. The composites of the invention may be used inplace of currently used materials, such as lithium niobate, in most typeof integrated optics devices, optical computing applications, opticalcommunication systems. For instance, the composites of the invention canbe used in to fabricate switches, modulators, waveguides, or otherelectro-optical devices.

For example, in optical communication systems devices fabricated fromthe composites of the invention can be incorporated into routers foroptical communication systems or waveguides for optical communicationsystems or for optical switching or computing applications. Because thecomposites of the invention are generally less demanding than currentlyused materials, devices made from such composites may be more highlyintegrated, as described in U.S. Pat. No. 6,049,641, which isincorporated herein by reference. Additionally, the composites of theinvention can be used in periodically poled applications as well ascertain displays, as described in U.S. Pat. No. 5,911,018, which isincorporated herein by reference.

Techniques to prepare components of optical communication systems fromoptically transmissive materials have been previously described, and canbe utilized to prepare such components from the composites provided bythe present invention. Many articles and patents describe suitabletechniques, and reference other articles and patents that describesuitable techniques, where the following articles and patents areexemplary:

L. Eldada and L. Shacklette, “Advances in Polymer Integrated Optics,”IEEE Journal of Selected Topics in Quantum Electronics, Vol. 6, No. 1,pp. 54-68 (January/February 2000); E. L. Wooten, et al. “A Review ofLithium Niobate Modulators for Fiber-Optic Communication Systems,” IEEEJournal of Selected Topics in Quantum Electronics, Vol. 6, No. 1, pp.69-82 (January/February 2000); F. Heismann, et al. “Lithium niobateintegrated optics: Selected contemporary devices and systemapplications,” Optical Fiber Telecommunications III B, Kaminow and Koch,eds. New York: Academic, pp. 377-462 (1997); E. Murphy, “Photonicswitching,” Optical Fiber Telecommunications III B, Kaminow and Koch,eds. New York: Academic, pp. 463-501 (1997); E. Murphy, IntegratedOptical Circuits and Components: Design and Applications, New York:Marcel Dekker (August 1999); L. Dalton et al., “Polymeric Electro-opticModulators: From Chromophore Design to Integration with SemiconductorVery Large Scale Integration Electronics and Silica Fiber Optics,” Ind.Eng. Chem. Res., Vol. 38, pp. 8-33 (1999); L. Dalton et al., “Frommolecules to opto-chips: organic electro-optic materials,” J. Mater.Chem., Vol. 9, pp. 1905-1920 (1999); I. Liakatas et al., “Importance ofintermolecular interactions in the nonlinear optical properties of poledpolymers,” Applied Physics Letters, Vol. 76, No. 11, pp. 1368-1370 (13Mar. 2000); C. Cai et al., “Donor-Acceptor-Substituted PhenylethenylBithiophenes: Highly Efficient and Stable Nonlinear OpticalChromophores,” Organic Letters, Vol. 1, No. 11 pp. 1847-1849 (1999); J.Razna et al., “NLO properties of polymeric Langmuir-Blodgett films ofsulfonamide-substituted azobenzenes,” J. of Materials Chemistry, Vol. 9,pp. 1693-1698 (1999); K. Van den Broeck et al., “Synthesis and nonlinearoptical properties of high glass transition polyimides,” Macromol. Chem.Phys. Vol. 200, pp. 2629-2635 (1999); H. Jiang, and A. K. Kakkar,“Functionalized Siloxane-Linked Polymers for Second-Order NonlinearOptics,” Macromolecules, Vol. 31, pp. 2501-2508 (1998); A. K.-Y. Jen,“High-Performance Polyquinolines with Pendent High-TemperatureChromophores for Second-Order Nonlinear Optics,” Chem. Mater., Vol. 10,pp. 471-473 (1998); “Nonlinear Optics of Organic Molecules andPolymers,” Hari Singh Nalwa and Seizo Miyata (eds.), CRC Press (1997);Cheng Zhang, Ph.D. Dissertation, University of Southern California(1999); Galina Todorova, Ph.D. Dissertation, University of SouthernCalifornia (2000); U.S. Pat. Nos. 5,272,218; 5,276,745; 5,286,872;5,288,816; 5,290,485; 5,290,630; 5,290,824; 5,291,574; 5,298,588;5,310,918; 5,312,565; 5,322,986; 5,326,661; 5,334,333; 5,338,481;5,352,566; 5,354,511; 5,359,072; 5,360,582; 5,371,173; 5,371,817;5,374,734; 5,381,507; 5,383,050; 5,384,378; 5,384,883; 5,387,629;5,395,556; 5,397,508; 5,397,642; 5,399,664; 5,403,936; 5,405,926;5,406,406; 5,408,009; 5,410,630; 5,414,791; 5,418,871; 5,420,172;5,443,895; 5,434,699; 5,442,089; 5,443,758; 5,445,854; 5,447,662;5,460,907; 5,465,310; 5,466,397; 5,467,421; 5,483,005; 5,484,550;5,484,821; 5,500,156; 5,501,821; 5,507,974; 5,514,799; 5,514,807;5,517,350; 5,520,968; 5,521,277; 5,526,450; 5,532,320; 5,534,201;5,534,613; 5,535,048; 5,536,866; 5,547,705; 5,547,763; 5,557,699;5,561,733; 5,578,251; 5,588,083; 5,594,075; 5,604,038; 5,604,292;5,605,726; 5,612,387; 5,622,654; 5,633,337; 5,637,717; 5,649,045;5,663,308; 5,670,090; 5,670,091; 5,670,603; 5,676,884; 5,679,763;5,688,906; 5,693,744; 5,707,544; 5,714,304; 5,718,845; 5,726,317;5,729,641; 5,736,592; 5,738,806; 5,741,442; 5,745,613; 5,746,949;5,759,447; 5,764,820; 5,770,121; 5,76,374; 5,776,375; 5,777,089;5,783,306; 5,783,649; 5,800,733; 5,804,101; 5,807,974; 5,811,507;5,830,988; 5,831,259; 5,834,100; 5,834,575; 5,837,783; 5,844,052;5,847,032; 5,851,424; 5,851,427; 5,856,384; 5,861,976; 5,862,276;5,872,882; 5,881,083; 5,882,785; 5,883,259; 5,889,131; 5,892,857;5,901,259; 5,903,330; 5,908,916; 5,930,017; 5,930,412; 5,935,491;5,937,115; 5,937,341; 5,940,417; 5,943,154; 5,943,464; 5,948,322;5,948,915; 5,949,943; 5,953,469; 5,959,159; 5,959,756; 5,962,658;5,963,683; 5,966,233; 5,970,185; 5,970,186; 5,982,958; 5,982,961;5,985,084; 5,987,202; 5,993,700; 6,001,958; 6,005,058; 6,005,707;6,013,748; 6,017,470; 6,020,457; 6,022,671; 6,025,453; 6,026,205;6,033,773; 6,033,774; 6,037,105; 6,041,157; 6,045,888; 6,047,095;6,048,928; 6,051,722; 6,061,481; 6,061,487; 6,067,186; 6,072,920;6,081,632; 6,081,634; 6,081,794; 6,086,794; 6,090,322; and 6,091,879.

The foregoing references provide instruction and guidance to fabricatewaveguides from materials generally of the types described herein usingapproaches such as direct photolithography, reactive ion etching,excimer laser ablation, molding, conventional mask photolithography,ablative laser writing, or embossing (e.g., soft embossing). Theforegoing references also disclose electron acceptors and electrondonors that can be incorporated into the compounds of the invention.

Components of optical communication systems that may be fabricated, inwhole or part, with the composites of the invention include, withoutlimitation, straight waveguides, bends, single-mode splitters, couplers(including directional couplers, MMI couplers, star couplers), routers,filters (including wavelength filters), switches, modulators (opticaland electro-optical, e.g., birefringent modulator, the Mach-Zenderinterferometer, and directional and evanescent coupler), arrays(including long, high-density waveguide arrays), optical interconnects,optochips, single-mode DWDM components, and gratings. The composites ofthe invention described herein may be used with, for example,wafer-level processing, as applied in, for example, vertical cavitysurface emitting laser (VCSEL) and CMOS technologies.

In many applications, the composites of the invention described hereinmay be used in place of lithium niobate, gallium arsenide, and otherinorganic materials that currently find use as light-transmissivematerials in optical communication systems.

The composites of the invention described herein may be used intelecommunication, data communication, signal processing, informationprocessing, and radar system devices and thus may be used incommunication methods relying, at least in part, on the opticaltransmission of information. Thus, a method according to the presentinvention may include communicating by transmitting information withlight, where the light is transmitted at least in part through amaterial including a composites of the invention.

The composites of the present invention can be incorporated into variouselectro-optical devices. Accordingly, in another aspect, the inventionprovides electro-optic devices including the following:

an electro-optical device comprising a composite of the invention;

a waveguide comprising a composite of the invention;

an optical switch comprising a composite of the invention;

an optical modulator comprising a composite of the invention;

an optical coupler comprising a composite of the invention;

an optical router comprising a composite of the invention;

a communications system comprising a composite of the invention;

a method of data transmission comprising transmitting light through orvia a composite of the invention;

a method of telecommunication comprising transmitting light through orvia a composite of the invention;

a method of transmitting light comprising directing light through or viaa composite of the invention;

a method of routing light through an optical system comprisingtransmitting light through or via a composite of the invention;

an interferometric optical modulator or switch, comprising: (1) an inputwaveguide; (2) an output waveguide; (3) a first leg having a first endand a second end, the first leg being coupled to the input waveguide atthe first end and to the output waveguide at the second end; and 4) anda second leg having a first end and a second end, the second leg beingcoupled to the input waveguide at the first end and to the outputwaveguide at the second end, wherein at least one of the first andsecond legs includes a composite of the invention;

an optical modulator or switch, comprising: (1) an input; (2) an output;(3) a first waveguide extending between the input and output; and (4) asecond waveguide aligned to the first waveguide and positioned forevanescent coupling to the first waveguide; wherein at least one of thefirst and second legs includes a composite of the invention. Themodulator or switch may further including an electrode positioned toproduce an electric field across the first or second waveguide;

an optical router comprising a plurality of switches, wherein eachswitch includes: (1) an input; (2) an output; (3) a first waveguideextending between the input and output; and (4) a second waveguidealigned to the first waveguide and positioned for evanescent coupling tothe first waveguide; wherein at least one of the first and second legsincludes a composite of the invention. The plurality of switches mayoptionally be arranged in an array of rows and columns.

The following description further illustrates the chromophore compoundsof the invention, films or composites that include the compounds, the EOactivity of the compounds, films or composites, and methods for makingand using the compounds, films or composites.

AJL8 is a model compound to study the thermal decomposition pathway ofdipolar chromophores. AJL8 exhibits a relatively large molecularhyperpolarizability (β values around 4,000×10⁻³⁰ esu). By doping 25 wt %of AJL8 into an amorphous polycarbonate (APC), the guest-host polymercan be poled at about 150° C., leading to a moderate r₃₃ value of about50 pm/V with good temporal stability at 85° C. Because of the reasonablenonlinearity and stability in AJL8/APC system, this material can be usedin conventional E-O devices. However, the thermal stability of AJL8-typechromophores has never been thoroughly studied for temperatures greaterthan 200° C.

The chemical structure of AJL8 contains a strong dialkylamino donor andCF₃-TCF acceptor. Because of its strong charge transfer nature, thistype of molecules is susceptible to reactions withnucleophilic/electrophilic moieties and diene/dienophile (see FIG. 1).Previously, it was found that dialkylamino donor tends to decomposeunder high temperatures due to its nucleophilicity and α-hydrogensadjacent to the nitrogen. Chemical sensitivities of this chromophorecould be further spotted along its π-conjugation bridge, such as thereactivity of the electron-rich vinylthiophene-based butadiene fromC_(a) to C_(d), the electrophilicity of C_(e), and the reactivity ofelectron-deficient double bonds at the acceptor end (see FIG. 2). Theseconsiderations give rise to the complexity of the chromophore'sdecomposition pathways at high temperatures.

Thermal stability of AJL8 has been studied earlier by differentialscanning calorimetry (DSC). At a heating rate of 10° C./min undernitrogen atmosphere, AJL8 was found to start to decompose at temperatureabove its melting point (192° C.) (see FIG. 3). The thermally induceddecomposition can be quantified by programmed thermal gravimetricanalysis (TGA). The weight loss of the compound was very minimal (<1 wt%) initially during the first 15-20 min of temperature ramping up, andthen started to increase nonlinearly with the time of isothermalannealing (see FIG. 4). The relative rate of weight loss is highlytemperature dependent, and the decomposition of compound is much fasterunder higher annealing temperatures. Surprisingly, even at a temperatureof 180° C. which is lower than its melting point, an about 5 wt % weightloss has already been observed after 30-min of isothermal annealing.This level of weight loss indicates non-negligible chromophoredecomposition, which has been verified by thin layer chromatography(TLC).

The crystalline AJL8 sample was first isothermally heated at 200° C. for5 min. After cooling under N₂ to room temperature, the residual samplestill has good solubility in common organic solvents, allowing thedecomposed products to be analyzed by TLC, UV-vis-NIR, ¹H NMR, and massspectrometry. Harsher curing conditions, such as higher temperature orlonger curing time, often gave insoluble solids, which may be thepolymerized byproducts after thermolysis. The testing provide usefulinformation about the critical pathway of AJL8 thermal decomposition.

The absorption spectrum of the cured samples measured in THF is quitedifferent from that of the pristine AJL8. The absorption maximum(λ_(max)) has blue-shifted for about 80 nm, which is close to that of amuch shorter chromophore 1 (see FIG. 5). Indeed, the cured productcontains 1 as the major component (about 60%), which was verified by thecombined analysis of TLC, ¹H NMR, and mass spectrometry.

The scheme of tandem DA and retro-DA reactions as the primarydecomposition pathway for AJL8 chromophore is schematically illustratedin FIG. 1. Referring to FIG. 1, two AJL8 molecules dimerize to form a DAadduct 2; the metastable compound 2 undergoes 1,3-sigmatropicrearrangement to give compound 3 having a regenerated thiophene ring;and under elevated temperatures, compound 3 is subject to retro-DAreaction to afford the truncated chromophore 1. The decompositionpathway is supported by the following experimental evidence: (1)analysis of the mass spectrum of decomposed products by electrosprayionization showed three distinct peaks with the charge/mass ratio (m/z)values corresponding to species 1 (100), AJL8 (55), 4 (10) or itsisomers and 2 or 3 (trace), respectively, (the numbers in theparentheses are the relatively intensities of peaks); (2) large dipolemoment chromophores like AJL8 tend to pack anti-parallel, whichfacilitates intermolecular DA cycloaddition reaction; (3) the s-cisconformer, with respect to C_(b)-C_(c), can be formed through σ-bondrotation at elevated temperatures to induce some reactivity of AJL8 atthe butadiene structure from C_(a) to C_(d) (see FIG. 2); (4) compound 1is unlikely the homolysis product of AJL8, due to the fact that nearlyno weight loss has been observed during sample preparation and thethermal activation energy at the curing temperature of 200° C. is farbelow the bond dissociation energy of the molecule; and (5) more rapidchromophore decomposition is expected once such pathway is initiated andgenerates unstable species such as 2, 3, and 4 causing avalanche-likechromophore decomposition.

The present invention provides a solution to the thermal instability ofcertain chromophore compounds by providing chromophores havingreinforced site isolation via controlled lattice hardening in E-Odendrimers and polymers. The present invention provides crosslinkabledendritic molecular glasses, in which the anthracene-acrylate-basedDiels-Alder (DA) cycloaddition (4+2) is employed as a protocol forhigh-temperature lattice hardening. The resultant dendrimers possess ahigh-density of chromophores that, while initially prone to thermaldecomposition in their individual soft forms, can be converted intothermally stable networks through DA crosslinking. More importantly, thedynamic phase transition is compatible with the poling process. Afterpoling, these materials have large E-O coefficients (up to 84 pm/V) andare stable up to 200° C. for 30 min of thermal excursion. The dendrimersalso showed impressive long-term stability at 150° C. for more than 200hr. This exceptional result provides an effective route to improvethermal stability of highly efficient chromophores by reinforced siteisolation.

The present invention provides anthracene-acrylate-based Diels-Alderlattice hardening for reinforced site-isolation in crosslinkabledendrimers. Site isolation of chromophores provided by NLO dendrimersand dendronized polymers has been adapted to overcome their strongelectrostatic interaction to achieve good poling efficiency. DA latticehardening is by far one of the most adaptable schemes to crosslink thesematerials to enhance temporal stability. In the present invention, thesite isolation effect is enhanced by high temperature DA latticehardening in order to sustain over 200° C. or beyond heating and tosuppress the possible bimolecular reaction pathway of chromophoredecomposition.

Representative DA crosslinkable E-O dendrimers of the invention areillustrated in FIG. 6 (see compounds 5 and 6). Compound 5 isfunctionalized with four anthryl groups at the periphery. Triacrylatemonomer (TAC) (see FIG. 6) was used as the dienophile crosslinkingagent. TAC has excellent compatibility with compound 5, and a 1:1 binarymixture of 5 and TAC (hereafter 5/TAC, FIG. 7) is highly amorphous. Theformulated solution of 5/TAC was spin-coated onto glass andindium-tin-oxide (ITO) substrates to form high optical quality filmswith micron thickness. The onset temperature (T_(x)) of theanthracene-acrylate-based DA crosslinking reaction is around 120° C.,which is close to its glass transition temperature (T_(g)). Incomparison, the composite of 5/TMI (TMI, trismaleimide crosslinkingagent) tends to form gel in a fairly low temperature range (from ambienttemperature to 65° C.) within a few hours due to high reactivity ofanthracene-maleimide-based DA cycloaddition. Because TAC is adeactivated dienophile compared to TMI, it reduces the temperature gapbetween T_(x) and T_(g) to facilitate processing. This providessignificant advantages for using the 5/TAC system, including more easilycontrolled poling processes, higher poling efficiency, and longerstorage time for unpoled films.

More importantly, the results from DSC showed that the onsetdecomposition temperature (T_(dec) in second heating) of 5/TAC is about60° C. higher than that of compound 5, indicating improved thermalstability of materials after crosslinking (see FIG. 7). Thermalstability of 5/TAC and compound 5 were compared at differenttemperatures by measuring the absorption spectra of thin films afterisothermal heating (to quantitatively follow possible chromophoredecomposition). Excellent thermal stability of 5/TAC was observed. Thethin films of 5/TAC showed <10% of decrease in absorbance after beingcured at 200-230° C. for 30 min (see FIG. 8) as opposed to about 75% ofabsorbance decrease when only compound 5 was cured at 200° C. for 5 min(see FIG. 9). The curing time for compound 5 has to be reduced to only 5min at each specified temperature interval in order to detect sensibleabsorbance change of the chromophore prior to its completedisappearance. All cured films of 5/TAC possessed solvent resistancetoward THF, 1,1,2-trichloroethane (TCE), and acetone. Upon curing, theintensity of typical anthryl absorption bands located at 350, 370, and390 nm also decreased considerably, suggesting efficiency of DA latticehardening via the anthracene-acrylate protocol of the invention.

Replacing TAC with dendrimer 6 provided an equivalent binary mixture ofcompounds 5/6, which contains a much higher chromophore loading level(39 wt %) than that of the 5/TAC (23 wt %). DSC showed that the onsetdecomposition temperature of 6 is ˜175° C., which is not surprising dueto thermal-induced radical polymerization of the periphery acrylates.However, by the same DSC analysis and isothermal heating shown above,crosslinked 5/6 exhibited increased thermal stability at hightemperatures up to 230° C., which was comparable to that of 5/TAC. Theseresults systematically prove that reinforced site isolation via DAlattice hardening dramatically improves the thermal stability of E-Odendrimers that contain high concentrations of AJL8-type chromophores.

To study poling and E-O property of these dendrimers, TCE solutions of5/TAC and 5/6 (with 9 wt % solid content) were filtered through a 0.2 μmsyringe filter, and spin-coated onto ITO-coated glass substrates toafford micron-thick films with good optical quality. The selected ITOsubstrate has suitable conductivity, low reflectivity, and transparencyfor poling and E-O measurement of these thin film samples. The filmswere baked at 60° C. under vacuum overnight, then a thin layer of goldwas sputtered onto the films as top electrode for contact poling. Thesequential curing and poling process were applied to the samples.Typically, the samples were annealed at temperatures about 100-120° C.to initiate partial crosslinking of the binary mixture 5/TAC or 5/6.Annealing enhances the dielectric strength of materials prior tosequential curing/poling process at elevated temperatures. Duringannealing, only low voltages of about 10-20 V/μm were applied. Then, thetemperature was ramped to 180-200° C. at a rate of 5° C./min, while thesignificantly improved dielectric properties of films allow much highervoltages of up to 150-170 V/μm to be applied sequentially. Finally, thesamples were cooled to room temperature and the poling field wasremoved. The r₃₃ values of poled films were measured by using themodified Teng-Man reflection technique at the wavelength of 1310 nm (C.C. Teng and H. T. Man, Appl. Phys. Lett., 1990, 56, 1734). The resultsare summarized in Table 1.

TABLE 1 Physical and optical properties of 5, 6, 5/TAC, and 5/6. Dye^(a)Thermal Poling Poling r₃₃ ^(e) Material Content λ_(max) ^(b) T_(g) ^(c)T_(x) ^(c) T_(dec) ^(c) stability^(d) Temp. Field (pm/V) Entries (wt %)(nm) (° C.) (° C.) (° C.) (%) (° C.) (MV/cm) at 1310 nm 5 32.0 776 155 —212 <10 — — — 6 49.0 700  85 — 175 <10 — — — 5/TAC 23.0 709 — 127 268 89120-182 1.0 44 5/6 39.0 708 — 112 270 89 130-200 0.9 84 ^(a)Net weightpercentage of chromophore within dendrimers. ^(b)The wavelengths of theabsorption maxima on thin film after curing. ^(c)Analytic results ofDifferential Scanning Calorimeter (DSC) at the heating rate of 10°C./min on thermo-equilibrate samples: T_(g), glass transitiontemperatures; T_(x), onset crosslinking temperatures; T_(dec), onsetdecomposition temperatures. ^(d)Residual percentage of chromophoresafter thin films were isothermally cured. The chromophore content wasquantified by the absorbance of films at λ_(max). Temperature/durationof curing: 230° C./30 min for 5/TAC and 5/6; 200° C./5 min for compounds5 and 6. ^(e)Electro-Optic coefficients measured at 1310 nm bysimple-reflection technique.

Relatively large r₃₃ values of 44 pm/V and 84 pm/V were obtained for5/TAC and 5/6, respectively, which are almost linearly proportional totheir chromophore content. This level of E-O activity is about 10-20%lower than those of the lower T_(g) crosslinkable dendrimers. Accordingto oriented gas model, the orientational factor of μE/(5 k_(B)T)decreases at much higher poling temperatures, where E represents thepoling field, k_(B) the Boltzmann constant, and T the polingtemperature. Both poled samples showed outstanding results at hightemperatures. For example, after the poled samples of 5/6 were exposedto thermal excursion at either 200° C. for 30 min or 150° C. for 200 hr,about 75% of the initial poling-induced r₃₃ values was maintained. Thisis the first example of organic spin-on materials showing better E-Oactivity and similar thermal stability compared the benchmark organic EOcrystal, DAST.

A representative DA crosslinkable compound of the invention thatincludes diene and dienophile crosslinkable groups is illustrated inFIG. 16. The physical properties of the DA crosslinkable chromophore assummarized in Table 2.

TABLE 2 Physical properties of a representative DA crosslinkablechromophore. Dye Therm. content λ_(max) ^(b) T_(g) ^(c) T_(x) ^(c)T_(dec) ^(c) Stab.^(d) (wt %) (nm) (° C.) (° C.) (° C.) (%) 39 705 — 130273 90 ^(a)Net weight percentage of chromophore within dendrimers.^(b)Wavelengths of the absorption maxima on thin film after curing.^(c)Analytical DSC results at the heating rate of 10° C./min onthermo-equilibrate samples: T_(g), glass transition temperatures; T_(x),onset crosslinking temperatures; T_(dec), onset decompositiontemperatures. ^(d)After isothermal heating on thin film at 230° C. for30 min monitored by UV-vis-NIR.

The poled films described above prepared from DA crosslinkabledendrimers demonstrated large EO coefficients (up to 84 pm/V at 1310 nm)and process temporal stability at 200° C. for 30 min. However, thepreparation of well-defined dendrimers can be complicated and timeconsuming. Moreover, because of the poor dielectric strength of thebinary dendrimers, an annealing process is needed prior to thesequential curing/poling process at elevated temperatures to apply largeelectric fields for efficient poling. The difficulty of preparation andpoling process adds a significant complication toward practicalapplications. To overcome these deficiencies, the present inventionfurther provides ultrahigh thermally stable EO polymeric materials(crosslinked polymer composites) with a capacity of easy, low-costlarge-scale synthesis. Furthermore, because of the reasonable dielectricstrength of crosslinkable host polymers, a large external electric fieldcan be directly applied to the films to orient the dipolar chromophoresduring the poling. Compared to the DA crosslinkable dendrimers describedabove, the crosslinkable EO polymers not only show much simplifiedpoling process, but also lead to much higher poling efficiency (30-50%enhancement).

Crosslinkable polymer AJL4B was prepared through the Steglichesterification using 1,3-dicyclohexylcarbodiimde (DCC) as thecondensation reagent between appropriate 9-anthracenepropanoic acid andpendant phenolic group of the high-T_(g) alternating polymers. The FT-IRspectrum of the resultant anthracenyl-functionalized polymer AJL4Bclearly shows a lack of phenol absorbance at about 3200 cm⁻¹ compared tothe original polymer, which indicates the complete termination ofphenolic groups. Gel-permeation chromatography (GPC) reveals anumber-average molecular weight (M_(n)) of about 25 000 for theresultant polymers. Thermal analysis by differential scanningcalorimetry (DSC) shows a relatively high glass transition temperature(T_(g)) of 215° C. for AJL4B (ramping rate, 10° C./min, under nitrogen).PMMA-AMA30 (poly[(methyl methacrylate)-co-(9-anthracenyl methylmethacrylate)] with around 30 mol % of the anthracenyl moiety) wasobtained from the radical polymerization at the presence of AIBN. TheDSC study shows a moderately high T_(g) of 135° C. The structures ofanthracenyl-containing crosslinkable polymers PMMA-AMA30 and AJL4B areillustrated in FIGS. 12A and 12B, respectively.

Representative crosslinked chromophores systems (crosslinked polymercomposites) were prepared by reaction of the anthracenyl-containingcrosslinkable polymers with DA crosslinkable dendritic chromophores(AJLS109, 113, 114), each having a first-generation dendron capped withacrylate moiety at both donor site and bridge site. FIG. 13 is aschematic illustration of the preparation of the representativecrosslinked chromophores systems (crosslinked polymer composites).

The anthracenyl-containing crosslinkable polymers show goodcompatibility with the relatively high polar DA crosslinkable dendriticchromophores. To study the chromophoric absorptivity and stability insolid states, DA crosslinkable dendritic chromophore compounds AJLS109,113, and 114 were mixed into a solution with PMMA-AMA30 or AJL4B in1,1,2-trichloroethane. By controlling the 1:1 molar ratio of anthracenyland acrylate moieties in the composite, the net chromophore content ofpolymer composites containing AJLS109 and AJLS114 was about 16-17 wt %,and that of polymer composites containing AJLS113 was 12 wt %. Thesesolutions were spin-coated onto glass and ITO substrates and bakedovernight at 50° C. in vacuum oven to afford thin films, respectively.The films showed good mechanical strength, and were optically smooth anduniform upon visual inspection by optical microscopy. The DSC studyshowed the onset temperature (T_(x)) of the anthracene-acrylate-based DAcrosslinking reaction in the polymer composites is around 120° C., whichis in line with that of the DA crosslinkable dendritic chromophores.More importantly, the results from DSC showed the similar performance onprolonging the chromophore stability (onset decomposition temperature(T_(dec) in second heating) of material composites is up to 270° C.) asdendrimer systems, clearly indicative of improved thermal stability ofmaterials after crosslinking. Thermal stability of polymer compositeswas investigated by measuring the absorption spectra of thin films afterisothermal heating at different temperatures, which was toquantitatively follow the possible chromophore decomposition. It shouldbe noted that the intensity of typical anthracenyl absorption bandslocated in 350, 370, 390 nm decreased considerably, indicating the goodefficiency of DA lattice hardening. All thin films composed ofPMMA-AMA30 and AJL4B showed <10% of decrease in absorbance after beingcured at 200° C. for 30 min (see FIG. 14, crosslinked polymer compositePMMA-AMA30; FIG. 15, crosslinked polymer composite PMMA-AMA30 andPMMA-AMA30 and AJLS114), while the absorbance of DA crosslinkabledendritic chromophores AJLS109, 113, and 114 showed nearly completedisappearance after being cured at 150° C. for 15 min. The decolorphenomena are primarily attributed to the thermal-induced radicalpolymerization of the peripheral acrylate moieties.

To study poling and E-O properties of the crosslinked polymercomposites, 9 wt % solutions of DA crosslinkable dendritic chromophorecompounds AJLS109, AJLS113, and AJLS114 and crosslinkableanthracenyl-containing polymers PMMA-AMA30 or AJL4B in1,1,2-trichloroethane were formulated, filtered through a 0.2-μm PTFEsyringe filter, and spin-coated onto ITO substrates. The loading ratiowas selected to keep equal equivalent of anthryl and acrylate groups inthe material composites. After baking overnight at 60° C. under vacuumto remove the residual solvent completely, a thin layer of gold wassputtered onto the films as the top electrode for contact poling. Bothpoling fields and currents were monitored to optimize the entireprocess. It is worth noting that compared to previous dendrimer samples,which need a critical annealing process at temperatures about 100-120°C. prior to the poling process with large external applied electricfields to obtain enhanced dielectric strength, the sequentialcuring/poling can be performed straightforwardly due to the reasonabledielectric strength from the host polymers. After cooling to roomtemperature and removing the poling field, r₃₃ values of the poled/curedfilms were measured using the Teng-Man simple reflection technique atthe wavelength of 1.31 μm. The poling conditions and measured r₃₃ valuesof these polymers are tabulated in Table 2. Comparable large r₃₃ valuesof 42 pm/V and 86 pm/V were obtained for PMMA-AMA30/AJLS109 andPMMA-AMA30/AJLS114, respectively. Considering the much lower chromophorecontent relative to that of the DA crosslinkable dendritic chromophores,these crosslinked polymer composites show greater poling efficiencyabout 30-50%. Furthermore, crosslinked polymer composites based onhigher T_(g) polymer of AJL4B demonstrate relatively lower r₃₃ values of33 pm/V and 68 pm/V for AJL4B/AJLS109 and AJL4B/AJLS114, respectively,which can be ascribed to the decreasing orientational factor withincreasing poling temperature in the oriented gas model.

Moreover, the poled samples showed temporal stability at hightemperatures. For example, after the poled samples of AJL4B/AJLS109 andAJL4B/AJLS114 were exposed to thermal excursion at 150° C. for 5 hrs,around 85% of the initial poling-induced r₃₃ values were still retainedin virtue of the site isolation effect via effective DA crosslinkingreactions. As for PMMA-AMA30, even though it original T_(g) is 135° C.,after the thermal curing/poling, the samples show high temporalstability of oriented acentric polar order after exposed to thermalexcursion at 150° C. for 30 min. This result can be attributed to thelattice hardening from the effective anthracene-acrylate reactions.

The physical and EO properties of representative crosslinked polymercomposites is summarized in Table 3.

TABLE 3 Physical and E-O properties of crosslinked polymers composites.Dye T_(g) ^(c) Thermal Poling Poling r₃₃ ^(f) Host NLO Content λ_(max)(° C.) T_(dec) ^(c) stability^(d) Voltage Temp. (pm/V) PolymerChromophore (wt %)^(a) (nm)^(b) Host Guest (° C.) (%) (V/μm)^(e) (°C.)^(e) @ 1.31 μm PMMA- 109 16.7 704 85 258 93 100 160 42 AMA30 114 17.5769 135 77 253 95 110 160 86 113 11.9 653 68 261 93 100 147 12 AJL4B 10916.4 707 85 257 92 100 195 33 114 17.2 772 215 77 — 90 100 185 68^(a)Net weight percentage of chromophore within dendrimers.^(b)Wavelengths of the absorption maxima. ^(c)Analytic results of DSC atthe heating rate of 10° C./min on thermo-equilibrate samples: T_(g),glass transition temperatures; T_(dec), onset decompositiontemperatures. ^(d)Residual percentage of chromophore after thin filmswas isothermally cured. The chromophore content was quantified by theabsorbance of the film at λ_(max). Duration of curing: 30 min. ^(e)Allthe poling studies were performed by applying the full voltages at thebeginning, then ramped the temperature from 40° C. to the optimal polingtemperatures at the heating rate of 10° C./min. ^(f)Electro-opticcoefficients measured by simple-reflection technique.

Through rational material design, a series of highly efficient,crosslinked polymer composites have been designed and synthesized basedon the anthracene-acrylate-based DA crosslinking reaction. Tworepresentative anthracenyl-containing polymers (PMMA-AMA30 and AJL4B)with different glass transition temperatures demonstrated effectivelattice hardening in prolonging the thermal stability and temporalstability of the oriented polar order. The results show the chemistry oflattice hardening is compatible with the poling process in polymercomposites based on both distinct polymers, and also enhances thethermal stability of dipolar chromophores and poling-induced acentricorder parameter up to 200-230° C. More importantly, these crosslinkedpolymer composites show a promising potential in device applications invirtue of the easy processability, high reproducibility, and high polingefficiency compared to previous analogues based on DA crosslinkabledendritic chromophores.

The present invention provides DA crosslinkable dendritic chromophoresfunctionalized with anthracenyl and acrylate moieties that can performDiels-Alder cycloaddition to fulfill the protocol for high-temperaturelattice hardening. These chromophores with high density of standardizedAJL8-type chromophores that are prone to thermo-decomposition in theirthermoplastic form, can be converted into thermally stable networks toprovide excellent site isolation of chromophores. After poling, large EOcoefficients (up to 84 pm/V at 1310 nm) can be obtained in thesedendrimers. These poled dendrimers maintain their alignment stability at200° C. for 30 min and also possess impressive long-term stability at150° C. for more than 200 hrs. This is the first example of organicspin-on materials that shows better EO activity and thermal stabilitythan the benchmark organic EO crystal, DAST. The present invention alsoprovides an effective molecular engineering approach to systematicallyincrease thermal stability of highly polarizable dipolar chromophoresfor high temperature on-chip applications.

The following examples are provided for the purpose of illustrating, notlimiting, the invention.

EXAMPLES

General methods. ¹H and ¹³C NMR spectra were recorded on Bruker 300 and500 spectrometers, respectively, with CDCl₃ as solvent andtetramethylsilane (TMS) as an internal standard unless otherwisespecified. Absorption spectra were obtained with a Perkin-Elmer Lambda-9spectrophotometer. ESI-MS spectra were recorded on a Bruker DaltonicsEsquire ion trap mass spectrometer. Glass transition temperatures(T_(g)) were measured by differential scanning calorimetry (DSC) using aDSC2010 in TA instruments with a heating rate of 10° C./min.

Materials. Dichloromethane (CH₂Cl₂), acetone and tetrahydrofuran (THF)were distilled over phosphorus pentoxide and sodium benzophenone ketyl,respectively under nitrogen prior to use. A10 was prepared according tothe methods described in the literature. All other chemicals, includingA1, A3, A6, A7, and A9, were purchased from Aldrich and were usedwithout further purification. All reactions were carried out under aninert atmosphere unless otherwise specified.

Example 1 Preparation of Representative Dendritic CrosslinkableChromophore Compounds

In this example, the preparation of representative dendriticcrosslinkable chromophore compounds of the invention is described. Thepreparation of dendrons useful in the preparation of the dendriticcompounds is illustrated schematically in FIG. 10. The preparation ofthe representative dendritic compounds is illustrated schematically inFIG. 11.

Compound A2. The suspension of 9-methanolanthracene (compound A1, 6 g,29 mmol) in toluene was cooled to 0° C. followed by addition ofphosphorus tribromide (3.2 mL, 33.6 mmol) by syringe carefully undernitrogen. The mixture was kept stirring at 0° C. for 1 h and then warmedup slowly to RT. After 3 h, the reaction was quenched by saturatedNa₂CO₃ solution carefully. After washed by water and brine, the organiclayer was dried by Na₂SO₄. After removing the solvent under reducedpressure, yellow crystal (compound A2) was obtained (7.5 g, 97%), whichwas used without further purification.

¹H NMR (400 MHz, CDCl₃): δ 856 (s, 1H), 8.36 (d, J=8.8 Hz, 2H), 8.08 (d,J=8.4 Hz, 2H), 7.67-7.48 (m, 4H), 5.54 (s, 2H).

Compound A4. To a solution of methyl 3,5-dihydroxylbenzoate (compoundA3, 1.54 g, 9.16 mmol), 9-bromomethylanthracene (compound A2, 6.0 g, 22mmol, 2.4 equiv) in freshly distilled acetone (40 mL) was addedpotassium carbonate (3.04 g, 22 mmol, 2.4 equiv) slowly and then thereaction mixture was heated to reflux and kept stirring overnight (After1 h, the reaction mixture turned transparent yellow). After the majorpart of solvent was removed, the reaction solution was cooled down to 0°C. for crystallization. The yellow needle-like solid was collected anddried in vacuum to afford pure compound A4 as a yellow solid (4.03 g,81%), mp 250-251° C. ¹H NMR (CDCl₃, TMS, δ ppm): 8.56(s, 2H), 8.31(d,J=9.0 Hz, 4H), 8.09(d, J=7.8 Hz, 4H), 7.61(s, 2H), 7.58˜7.49(m, 8H),7.10(s, 1H), 6.02(s, 4H), 3.97(s, 3H).

Compound A5. The solution of compound A4 (2.36 g, 4.32 mmol), potassiumcarbonate (1.80 g, 13 mmol) and MeOH/H₂O (30 mL+10 mL) was kept stirringat room temperature overnight, and then removed MeOH under reducedpressure. The reminder was dissolved with CH₂Cl₂, and the organic phrasewas washed with HCl (2M), brine and then dried over Na₂SO₄. The solventwas concentrated and purified using flash chromatography to afford thepure compound A5 (1.78 g, 3.3 mmol, 77%). ¹H NMR (DMSO, TMS, δ ppm):8.71(s, 2H), 8.39(d, J=8.7 Hz, 4H), 8.16(d, J=7.8 Hz, 4H), 7.63-7.53(m,8H), 7.36(s, 3H), 6.07(s, 4H). ¹³C NMR (DMSO, TMS, δ ppm): 167.01,160.00, 133.01, 130.95, 130.53, 128.94, 128.72, 127.01, 126.70, 1265.29,124.21, 108.46, 106.35, 62.60.

Compound A8. 47 mL of NaOH solution (5%, w/v) was taken in a 100 mL2-neck flask and deaerated by bubbling with dry N₂ for 30 min.3,5-dihydroxybenzoic acid (compound A7, 3.08 g, 20 mmol) was added intoreaction flask slowly. After 5 min with bubbling, acryloyl chloride(compound A6, 7.2 g, 80 mmol) in 10 mL of CH₂Cl₂ was added followed bykeeping stirring for another 1 h. The white precipitation (4.9 g, 94%)was collected via filtration. ¹H NMR (CDCl₃, TMS, δ ppm): 7.81(s, 2H),7.33(t, J=2.1 Hz, 1H), 6.69˜6.63(m, 2H), 6.39˜6.29(m, 2H), 6.10˜6.06(m,2H). ¹³C NMR: (CDCl₃, TMS, δ ppm): 170.32, 163.85, 150.97, 133.57,131.43, 127.31, 121.01, 120.87.

Compound TAC. 20 mL of NaOH solution (5%, w/v) was taken in a 100 mL2-neck flask and deaerated by bubbling with dry N₂ for 30 min.1,1,1-tris(4-hydroxyphenyl)ethane (compound A9, 1 g, 3.3 mmol) was addedinto reaction flask slowly. After 5 min with bubbling, acryloyl chloride(compound A6, 1.78 g, 19.8 mmol) in 10 mL of CH₂Cl₂ was added followedby keeping stirring for another 1 h. The white precipitation (1.3 g,86%) was collected via filtration. ¹H NMR (CDCl₃, TMS, δ ppm): 7.14(d,J=11.4 Hz, 6H), 7.08(d, J=11.7 Hz, 6H), 6.65˜6.59(m, 3H), 6.38˜6.29(m,3H), 6.04˜6.00(m, 3H). ¹³C NMR: (CDCl₃, TMS, δ ppm): 164.50, 148.84,146.14, 132.55, 129.70, 127.98, 120.90, 30.88.

Dendrimer 5. The solution of compound A10 (0.28 g, 0.50 mmol), compoundA5 (1.20 g, 2.24 mmol), and 4-dimethylamino-pyridine (DMAP, 0.02 g,0.176 mmol) in THF (15 mL) was kept stirring at room temperatureovernight after addition of1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride (EDC, 0.20g, 1.056 mmol) slowly under the nitrogen atmosphere. The solution waskept stirring for 24 h. After filtration of the resultant ureacarefully, all of the solvent was evaporated under reduced pressure. Thecrude product was purified by column chromatography using ethyl acetateand hexane (1:6, v/v) as the eluent to afford dendrimer 5 as a deepgreen solid (0.69 g, 85%). ¹H NMR (CDCl₃, TMS, δ ppm): 8.51(s, 2H),8.44(s, 2H), 8.22(d, J=8.7 Hz, 8H), 8.08-7.98(overlap, 9H),7.61-7.45(overlap, 26H), 7.31(d, J=9.0 Hz, 2H), 7.08(d, J=21.6 Hz, 2H),6.80(d, J=15.5 Hz, 1H), 6.71(d, J=8.5 Hz, 2H), 6.65(d, J=15.5 Hz, 1H),6.48(d, J=15.5 Hz, 1H), 5.92(s, 4H), 5.83(s, 4H), 5.10(s, 2H), 4.43(t,2H), 3.58(t, 2H), 3.36(m, 2H), 1.92(s, 3H), 0.94(t, J=6.9 Hz, 3H). ¹³CNMR: 175.17, 166.51, 166.07, 162.17, 160.60, 160.53, 154.13, 149.44,140.92, 140.74, 136.49, 136.39, 135.23, 132.05, 131.94, 131.60, 131.59,131.15, 131.13, 129.68, 129.41, 129.34, 126.89, 126.87, 126.47, 126.28,125.29, 125.26, 123.97, 123.91, 123.52, 123.01, 113.01, 112.11, 111.20,110.98, 110.67, 108.83, 108.58, 107.94, 107.45, 97.31, 63.21, 62.64,59.26, 58.78, 55.52, 48.09, 44.79, 29.91, 19.39, 12.37, 1.23. ESI-MS(m/z): Calcd: 1598.5; Found: 1599.6.

Dendrimer 6. The solution of compound A10 (0.7 g, 1.23 mmol), compoundA8 (0.74 g, 2.82 mmol), and 4-dimethylamino-pyridine (DMAP, 0.04 g, 0.35mmol) in THF (25 mL) was kept stirring at room temperature overnightafter addition of 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimidehydrochloride (EDC, 0.5 g, 2.65 mmol) slowly under the nitrogenatmosphere. The solution was kept stirring for 12 h at room temperature.After filtration of the resultant urea carefully, all of the solvent wasevaporated under reduced pressure. The crude product was purified bycolumn chromatography using ethyl acetate and hexane (1:3, v/v) as theeluent to afford dendrimer 6 as a deep green solid (1.23 g, 76%). ¹H NMR(CDCl₃, TMS, δ ppm): 8.09(d, J=15.6 Hz, 1H), 7.76(d, J=2.1 Hz, 2H),7.71(d, J=2.1 Hz, 2H), 7.57(s, 1H), 7.47(d, J=9.0 Hz, 2H), 7.27(d, J=3.3Hz, 2H), 7.20(d, J=3.3 Hz, 2H), 6.82(d, J=9.0 Hz, 2H), 6.68(m, 4H),6.60(d, J=15.6 Hz, 1H), 6.37(m, 4H), 6.09(m, 4H), 5.43(s, 2H), 4.452(t,2H), 3.77(t, 2H), 3.54(m, 2H), 1.95(s, 3H), 1.28(t, J=6.9 Hz, 3H). ¹³CNMR: 175.12, 164.85, 164.39, 163.88, 163.85, 162.43, 154.93, 151.10,151.00, 149.13, 146.36, 138.27, 136.41, 135.54, 133.75, 133.64, 131.91,131.39, 129.60, 129.55, 127.35, 127.28, 123.64, 123.26, 120.99, 120.71,120.61, 120.43, 120.35, 115.66, 112.19, 111.45, 111.18, 110.96, 110.60,97.46, 94.11, 93.85, 62.62, 59.20, 58.38, 48.57, 45.45, 19.18, 12.42.ESI-MS (m/z): Calcd: 1054.2; Found: 1054.8.

While illustrative embodiments have been illustrated and described, itwill be appreciated that various changes can be made therein withoutdeparting from the spirit and scope of the invention.

1. A compound having the formula (I):

wherein D is a π-electron donor group, A is a π-electron acceptor group,D₁ is a dendron moiety functionalized with one or more crosslinkablegroups, D₂ is a dendron moiety functionalized with one or morecrosslinkable groups, n is 0, 1, or 2, m is 0, 1, or 2, and m+n is ≧1,wherein the crosslinkable groups are independently selected from thegroup consisting of an anthracenyl group and an acrylate group.
 2. Thecompound of claim 1, wherein the crosslinkable groups are anthracenylgroups.
 3. The compound of claim 1, wherein the crosslinkable groups areacrylate groups.
 4. The compound of claim 1, wherein the crosslinkablegroups are anthracenyl groups and acrylate groups.
 5. The compound ofclaim 1, wherein D₁ and D₂ are independently selected from the groupconsisting of


6. The compound of claim 5, wherein D₁ is d1 and D₂ is d1.
 7. Thecompound of claim 5, wherein D₁ is d2 and D₂ is d2.
 8. The compound ofclaim 5, wherein D₁ is d1 and D₂ is d2.
 9. The compound of claim 5,wherein D₁ is d2 and D₂ is d1.
 10. A method for forming a film havingelectro-optic activity, comprising: (a) depositing first and secondcrosslinkable compounds onto a substrate to provide a film, wherein thefirst compound is a compound of claim 1, wherein the crosslinkable groupis an anthracenyl group, and wherein the second compound is a compoundof claim 1, wherein the crosslinkable group is an acrylate group; (b)applying an aligning force to the film at a temperature sufficient toprovide a film having at least a portion of the compounds aligned; (c)heating the film having at least a portion of the compounds aligned at atemperature sufficient to effect crosslinking between the first andsecond compounds; and (d) reducing the temperature of the film toprovide a hardened film having electro-optic activity.
 11. The method ofclaim 10 further comprising depositing a crosslinkable crosslinkingagent on the substrate.
 12. The method of claim 10 further comprisingdepositing a crosslinkable polymer on the substrate.
 13. A filmobtainable by the method of claim
 10. 14. A method for forming a filmhaving electro-optic activity, comprising: (a) depositing a compound ofclaim 1 onto a substrate to provide a film, wherein the compound ofclaim 1 has anthracenyl and acrylate crosslinkable groups; (b) applyingan aligning force to the film at a temperature sufficient to provide afilm having at least a portion of the compounds aligned; (c) heating thefilm having at least a portion of the compounds aligned at a temperaturesufficient to effect compound crosslinking; and (d) reducing thetemperature of the film to provide a hardened film having electro-opticactivity.
 15. The method of claim 14 further comprising depositing acrosslinkable crosslinking agent on the substrate.
 16. The method ofclaim 14 further comprising depositing a crosslinkable polymer on thesubstrate.
 17. A film obtainable by the method of claim
 14. 18. Anelectro-optic device, comprising the film of claim
 13. 19. Anelectro-optic device, comprising the film of claim 17.